When we first met, I was immediately impressed with Annie and the technical skills she had on day one, but during the time worked together, her understanding of data analysis and the tools of the trade grew far more than that of her peers.
The client was very impressed and complimentary of Suzzie.
A personal reference letter for your student, friend, or co-worker is not the space for exaggeration or falsities.
This is especially the case for professors.